Highly fluorinated aromatic compounds such as perfluorophenanthrene have a number of potential uses, including uses as precursors to fluorinated chemical intermediates for making fluorosurfactants and biologically active compounds, but the commercialization of such uses has been limited by the difficulty in synthesizing them. While it is relatively easy to synthesize perfluorocycloalkanes, it is much more difficult to make a highly fluorinated aromatic compound.
Perfluorinated aromatic compounds have been made by the complete exchange of perchloroaromatic compounds with a suitable source of fluoride ions such as KF or HF. This method is not efficient because it requires the synthesis of the chlorinated intermediate and in addition requires either a catalyst or anhydrous conditions. Potassium fluorie is very difficult to dry and while anhydrous hydrogen fluoride can be obtained, this reactant usually requires a catalyst.
It has been known for many years that perfluoro- or highly fluorinated cycloaliphatic compounds can be converted to fluorinated aromatic compounds by high temperature defluorination or dehydrofluorination. Gething, et al. "A New General Route to Aromatic Fluorocarbons", Nature (London) 183, pages 588-9 (1959) discloses that perfluoronaphthalene can be made from perfluorodecohydronaphthalene by defluorination at 400.degree.-600.degree. C. over iron gauze. Bailey, et al., "Fluorinations With Complex Metal Fluorides", J. of Fluorine Chemistry, 37, pages 1-14 (1987) reported defluorination of saturated cyclic fluorocarbons over fully spent cesium trifluorocobaltate at 400.degree. C. Attempts by others to effect reactions of perfluorinated aliphatic compounds have given complete defluorination to non-fluorine-containing products.
Johncock, et al. "The Semi-Micro Determination of Fluorine and Chlorine in Organic Compounds", Analyst, 84, pages 245-7 (1959) discloses that fluoro- and chlorofluoro compounds can be totally decomposed for analytical purposes by reaction with a biphenyl-sodium-dimethoxyethane complex. This author states that other aromatic compounds such as benzophenone and other ethers such as tetrahydrofuran have been tried but were rejected.
MacNicol and Robertson, Nature (London), 332, pages 59-61 (1988) states that saturated fluorocarbons are noted for outstanding chemical inertness, requiring extreme conditions such as treatment with metals at 500.degree. C. to react. These authors report, however, reacting perfluorodecahydronaphthalene with arenethiolate nucleophiles in a dipolar aprotic solvent to form organic products containing no fluorine and including octakis (phenylthio)naphthalene under ambient conditions as well as at temperatures in the range of 60.degree.-70.degree. C. It should be noted that no fluorinated aromatics or other fluorine containing organic products were reported.
U.S. Pat. No. 4,820,884 discloses a defluorination process for preparing unsaturated aliphatic or cycloaliphatic perfluorocarbons by contacting the corresponding perfluoroalkane with activated carbon at a temperature of from about 300.degree. to 500.degree. C.